Cytochrome denaturation

Denaturation horse heart cytochrome Denaturation whale myoglobin Denaturation a-chymotrypsinogen Precipitation sheep liver nucleoprotein at 40°C in 30 minutes... 

For many solubilized enzymes the greatest catalytic activity and/or changes in conformation are found at R < 12, namely, when the competition for the water in the system between surfactant head groups and biopolymers is strong. This emphasizes the importance of the hydration water surrounding the biopolymer on its reactivity and conformation [13], It has been reported that enzymes incorporated in the aqueous polar core of the reversed micelles are protected against denaturation and that the distribution of some proteins, such as chymotrypsine, ribonuclease, and cytochrome c, is well described by a Poisson distribution. The protein state and reactivity were found markedly different from those observed in bulk aqueous solution [178,179],... 

Qi et al. (1998) have demonstrated that ribonuclease A exhibits behavior like that of cytochrome c. The burst phase observed on dilution of Gdm HCl-denatured RNase A is mimicked exactly by reduced RNase A. The latter, when carboxamidomethylated to prevent oxidation, has a CD at 222 nm that is nearly independent of temperature and indicative of extensive unfolding at zero denaturant. 

The above observations provide a clear demonstration that cosolvents in selected ranges of concentration create reversible perturbations of protein similar to those induced by other modifiers. The reversibility of the cosolvent effect is a prerequisite to cosolvent use and will depend on the concentration of cosolvent, which in turn will vary markedly with the type of solvent used. For instance, polyols can be used at concentrations up to 8 Af while methanol at 3 M causes the appearance of a new absorption band (410 nm) and, after further increases in concentration, an irreversible conversion of cytochrome P-450 into P-420. Other aliphatic alcohols cause denaturation at much lower concentrations. 

Additives such as polyethylene glycol, cationic antibiotics, polymers, small uncharged molecules, and negatively charged proteins have been used extensively in order to avoid the denaturing of enzymes or to improve the sensitivity and operational stability of biosensors. DNA has been proposed as an additive to improve the response and stability of biosensors based on CP. The biomolecules studied, such as tyrosinase [93], peroxidase [94], cytochrome C [95], have been shown to improve its performance by using adsorbed DNA within CP as an additive. 

Electrochemistry of disulfide unit present in cytochrome c (cyt c) molecules on gold electrodes has also been reported [169]. Disulfide unit in cytochrome c is strongly adsorbed on Au electrodes and this slows down the electron-transfer rate to the heme group. More recently, Krylov et al. [170] have immobilized cytochrome c by self-assembling on the surface-modified Au electrodes. CV was applied to study how denaturation and renaturation of cytochrome c depend on the solution composition. 

Fusion of chymotrypsin-containing vesicles with vesicles containing the substrate Suc-Ala-Ala-Pro-Phe-pNA by addition of partially denatured Cytochrome C. 

Where within the mitochondria are specific enzymes localized One approach to this question is to see how easily the enzymes can be dissociated from mitochondria. Some enzymes come out readily under hypotonic conditions. Some are released only upon sonic oscillation, suggesting that they are inside the matrix space. Others, including the cytochromes and the flavoproteins that act upon succinate and NADH, are so firmly embedded in the inner mitochondrial membranes that they can be dissociated only through the use of non-denaturing detergents. 

Figure 16.9 The ratio of the effective calorimetric enthalpy to the enthalpy calculated by the van t Hoff method from optical measurements, plotted against the temperature of denaturation. The symbols represent the following proteins , metmyoglobin A, ribonuclease O, cytochrome c O, a-chymotrypsin , lysozyme. Reproduced by permission from P. L. Privalov, Adv. Prot. Chem., 33, 167 (1979).

Fig. 3. Axial ligands of the heme iron in hemoproteins. The imidazole ring of a histidyl residue is one of the axial ligands in myoglobin, hemoglobin, and cytochrome c. In native cytochrome c the sixth ligand is a methionyl residue of the polypeptide chain. In partially denatured cytochrome c, and in myoglobin and hemoglobin, a variety of ligands, some of which are shown in the figure, may bind to the sixth coordination site...

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